Controls of Cement Texture and Composition on Sandstone Mechanical Property Changes From Reaction With CO2-Rich Brine

Abstract

Mitigating anthropogenic CO₂ emissions via geologic carbon sequestration involves injection of CO₂ into transmissive reservoir rock. While significant effort has explored fluid-rock interaction in these environments, the coupling of reservoir perturbation induced by CO₂-driven cement alteration and the changed mechanical properties of the reservoir is largely unknown. We conducted flow-through experiments on Pennsylvanian Morrow B Sandstone cores from the Farnsworth Field in West Texas, USA. CO₂-rich brine flowed through poikilotopic calcite- and disseminated dolomite-cemented cores between 0.01 and 0.1 mL/min at 71°C and 4200 psi (29.0 MPa) pore fluid pressure. Pre-experimental ultrasonic velocity measurements indicated higher dynamic elastic moduli for the calcite-cemented cores. Outlet fluids were enriched in Ca, Mg, and Fe in the dolomite-cemented core experiments, and the increasing (Fe) or decreasing (Ca and Mg) trends suggest increasing and decreasing access to an Fe-rich phase and dolomite, respectively, through time. In addition, the permeability of the calcite-cemented core increased significantly, whereas dolomite-cemented cores changed little when interacting with CO₂-rich brine. Ongoing tests will involve post-experimental velocity measurements to monitor mechanical changes from experimental alteration. Furthermore, cylinder-splitting tests (Brazil tests) will be performed to measure the tensile strength of post-experimental samples, and results will be compared to cores that have not been reacted with CO₂-rich fluids. These experiments help determine the degree to which chemo-mechanical degradation of Morrow B sandstone cores varies with cement texture and composition and should be applicable to a wide range of current and prospective carbon sequestration sites.

Funding for this project is provided by the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) through the Southwest Regional Partnership on Carbon Sequestration (SWP) under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018